I have the BayAreaAT FMIC with HKS SSQV (non-adjustable) recirculated with 1" hose. the piping is 2.75 od (i think), which is what it came with and I know it is a bit big.
I have an Apex'i dual funnel filter on a 3" od straight intake.
CT27 from ATS.

I know this has to do with the FMIC/BPV because I read about it in an old thread, but I can't find the thread anymore.

Usually while cruising on the interstate around 0 to -10 InHg, I get a stutter from the engine that is sometimes pretty rough, but mostly annoying as hell. It also happens in city driving in the same vacuum range while gently letting off the throttle. So to avoid it i have to stay in deep vacuum in low gear or go on and off throttle constantly, from slight boost to less than -10 InHg.

I know it is because of pressure differentials causing the AFM to flap back and forth, causing the shaking. Is there any way to erase this problem? Or do I have to live with this annoying problem forever?

Grot

06-29-2009, 05:03 AM

i know if you have extra money you can do the gen 3 electronics upgrade, this elimanates the AFM altogether.

But other than that im not gonna be any help.

T-spoon

06-29-2009, 05:20 AM

Sure that's not related to adjusting the BOV? I don't see what it would have to do with having a FMIC as opposed to a TMIC with the same BOV.

Are you sure its not the AFM or TPS itself that has a dead spot? If it happens in the same rpm regardless of load or gear, it is probably that.

Is this the thread you were talking about:
http://www.celicatech.com/forums/showthread.php?t=9360&highlight=pressure+afm+fmic

If so, while the flapper door might work with this setup (I think it would be much more erratic than on the intake piping), the IAT (intake air temp) would be way off.

Lagos

06-29-2009, 06:38 AM

recirculate the bov.

T-spoon

06-29-2009, 06:45 AM

recirculate the bov.

I believe he does have it recirc, but I still think it sounds like a BOV adjustment issue, or else not related to the IC/BOV in any way.

Shadowlife25

06-29-2009, 09:08 AM

Gotta go with joe on this one. If it was related to the bov (which he said is recirculated) it would pretty much do it all the time off throttle. At least in my experience.
It does sound more like a mis-adjustment of the TPS to me. I had a "rough" spot that cleared up after getting the TPS into the correct ranges.

donteatbugs

06-29-2009, 08:34 PM

its the turbo, i had the same problem with my fmic and upgraded turbo, this is because the compressor is too big for the exhaust turbine and at the switch over point into boost is chokes. i replaced everything on my car and when i went back to a stock turbo it fixed the problem.

Smaay

06-29-2009, 08:56 PM

do you have a wideband O2? i bet your fuel settings are way off.

joe's gt

06-30-2009, 03:28 AM

its the turbo, i had the same problem with my fmic and upgraded turbo, this is because the compressor is too big for the exhaust turbine and at the switch over point into boost is chokes. i replaced everything on my car and when i went back to a stock turbo it fixed the problem.

I would make sure your tps is in spec, make sure there are no dead spots, and if it revs smoothly through the rpm range, I would try what Bugs said. Seems like a plausible explanation barring faulty components.

My question would be tho, why does this only occur with an FMIC? Cuz i got the CT27 with a TMIC and don't have this problem. Maybe this is where pressure differentials come into play? I'm confused. lol. I don't see how a turbo would perform any differently between an FMIC and TMIC?

I have perfect AFR's always in all conditions. When the shuddering happens the AFR fluctuates from lean to normal in the same frequency as the shudder, which makes sense if the AFM is moving back and forth causing the mixture to change

The problem only exists in the +-5 psi range, and is completely independent of rpm. The problem only occurs when I am not accelerating or not decelerating, and I am hovering within my stated vacuum/boost range. It is almost completely unavoidable on the interstate at 60+ mph when there is some sort of load on the engine and I stay within my stated vacuum/boost range. Even on a straight flat section of interstate the wind causes enough load to bring the needle close to 0, and if I continue without fluctuating the throttle, the car will buck some, then smooth out some, until load brings the needle back to near 0, and it will buck some more. Usually the bucking is just a shudder and not violent, but its annoying.

I'm almost certain it has something to do with the turbo spooling up a bit, filling the piping until the pressure is more than can pass through a partially open thottle, then it must escape through the turbo (if my BOV is not opening easily enough), and cause the AFM to close a bit. Once pressure equalizes, pressure starts to build up again, and the cycle repeats in rapid succession until I change the throttle opening or close it completely.

Would it solve this to have an easier opening BOV?
I fixed my bov closed one day to see if anything would change, and the problem remained the same. (I know the BOV was closed bacause I heard the tubo "gobble")

I think the reason this problem is absent with TMIC is becasue the piping is smaller and much shorter, leaving little room for much excess pressure to build up, or at least if it does, it happens at a faster frequency as to be unnoticed by the driver???

Well, anyone out there have any ideas? :wtf:

joe's gt

07-01-2009, 06:28 AM

I have heard of air filters that are open and exposed to turbulence and pressure differences in air causing erratic operation of air flow meters. Some guys put a flower pot around them to prevent the turbulence, but i've never heard of that issue with the 3sgte AFM. I think that problem is more prevalent with hot wire MAFs. idk man. good luck tho, i'm interested in this as well if I ever get the chance to do these mods.

Sang

07-02-2009, 12:35 PM

or else not related to the IC/BOV in any way.

This is my vote.

kungfoo2003

07-03-2009, 01:55 AM

I'm starting to think that the BayArea FMIC kit just has piping that is way too big (2.75" od). On AllTrac.net there is 2 members with the same problem as me. One has a stock ct26 and one has a TD06.

I think the piping just creates a void that the turbo has to spool up slightly to fill in the 0 to 10 inHG range, once pressure fills the system it reaches the bottleneck (partial throttle) and has nowhere to go because the SSQV can't open easily enough without a large enough pressure difference between piping and manifold, so it exits through the turbo compressor, causing the AFM to close slightly. This happening in quick succession would cause my problem.

Agree?

T-spoon

07-03-2009, 02:35 AM

I'm no expert, but I still don't see that being the case. Too large of an IC or piping should just add some lag to your spool if anything. I don't see why you'd get surge that would effect the AFM if it's not enough to actuate the BOV unless the BOV is not functioning properly, but even then, turbo cars without a BOV at all don't get stumbling or hesitation or improper AFM operation as a result of compressor surge. I really am having trouble believing the piping or IC is causing what you're talking about, but I could be wrong of course.

joe's gt

07-03-2009, 02:38 AM

I'm no expert, but I still don't see that being the case. Too large of an IC or piping should just add some lag to your spool if anything. I don't see why you'd get surge that would effect the AFM if it's not enough to actuate the BOV unless the BOV is not functioning properly, but even then, turbo cars without a BOV at all don't get stumbling or hesitation or improper AFM operation as a result of compressor surge. I really am having trouble believing the piping or IC is causing what you're talking about, but I could be wrong of course.

+1. But I unfortunately don't know the answer to your problem either.

Be sure to post back what it was when you saw it so future members who may have this problem won't fall into the same trap.

It would help so much if you still had your stock TMIC so you could just slap that back on and see if the problem persists.

kungfoo2003

07-03-2009, 08:08 PM

Can't really slap the top mount back on, my turbo is clocked.

I know its an issue with the FMIC kit, because the AllTrac member with the CT26 only had this problem show up after installing the BayArea FMIC kit. I think all the kits were made with the HKS flange also.

If you think about how I explain the problem, it makes sense that the SSQV does not open, because at partial throttle with very low vacuum in the intake manifold (boost gauge reading 0 to 10 inHG, connected to manifold) contrasted to pressure gradually building up in the intercooler piping, the conditions do not offer an opportunity for the valve to open at all.

Does anyone else have intercooler piping that is 2.75" od? Or does everyone have smaller?
What size cores are you all using as well?

joe's gt

07-03-2009, 09:18 PM

The piping diameter may be too big and causing erratic BOV operation. I really don't think its your AFM either, especially if its independent of rpm.

Don't know.

Until then, only extra input or making a change could yield a solution.

Trance4c

07-04-2009, 12:59 AM

A lot of times you will get that flutter from the wastegate. A FMIC seems to increase the issue, I believe its an issue after increasing the volume of the intake track vs the exhaust pulses. Very typical with an internally gated turbo.

Also, a lot of times when clocking these turbos, the bracket necessary gets in the way of the wastegate actuating as well.

What Bugs is talking about is Compressor surge, I don't think that's the issue here.

kungfoo2003

07-04-2009, 07:14 AM

A lot of times you will get that flutter from the wastegate. A FMIC seems to increase the issue, I believe its an issue after increasing the volume of the intake track vs the exhaust pulses. Very typical with an internally gated turbo.

Also, a lot of times when clocking these turbos, the bracket necessary gets in the way of the wastegate actuating as well.

What Bugs is talking about is Compressor surge, I don't think that's the issue here.

I see what you mean about the bracket for clocked turbos, however, the custom bracket I built has one problem...It holds the wastegate shut too hard, so that even without a boost controller i get constant 16 psi. wierd huh? Could it be that my wastegate needs to open easier??

It makes more sense, what you say about the intake tract versus the exhaust pulses. That might be something for me to consider. But if that were true, why do more people not have this issue?

Lagos

07-04-2009, 04:37 PM

I think that you are correct in thinking that this is fmic/bov related.
Now that I think about it, my car has a similar issue. Mine only happens on the highway, when i build a little bit of boost (say 5psi), and gently ease back on the gas, the car will buck a bit. It always seemed to me like this was happening because the bov was too tight (not too loose) and only blew off a small amount of boost when i ease of the gas. Ive gotten around this problem by adjusting my driving habits. I make sure to fully step off the gas to make the bov open more.

My piping is only 2.25in. At 2.75in I would think that you are getting a very exaggerated version of the same problem, because you are dealing with a much larger volume of air in your intercooler piping.

If you want to try another bov, Id look into the synchronic bov. That one seems to be the most responsive to small changes in throttle.

ChrisD

07-04-2009, 05:18 PM

i had this issue even on a wta intercooler. bucking, hesitation, and that sort of thing, was the #1 reason i went to a standalone EMS. I think it is somewhat to do with the finickyness of the AFM. Anything you can do to limit things that might cause the AFM issues would help. ie. ensure hoses are all clamped on well, recirculate the bov, etc.

Sean

07-04-2009, 05:41 PM

I have the same issue, in fact I have it so bad that it will pop out of 5th gear the engine will buck so hard.

I've learned to drive it so it doesnt do it, but it is annoying. My thoughts of what it is, its my BOV (HKS SSQV) venting to air, rich condition, backfire.

I have a T3/T4, with a tial 38mm, and a FMIC. I think standalone is the best fix for this unfortunetaly.

joe's gt

07-04-2009, 07:22 PM

Damn guys, I thought this whole bucking issue only occurred during cold starts. Now your saying it occurs with an FMIC while driving.

WOW!!! The AFM is more of a POS than I thought.

donteatbugs

07-04-2009, 08:06 PM

i tried 3 different bovs on my car and they all did the same thing, im pretty sure its not the bov. i didnt have the problem with the completely stock turbo, and an audi bypass valve, 2.5" pipes and fuge fmic. when i replaced my turbo the problem went away all together. i know its a pain to change and i swapped out everything else before the turbo, like afm, ecu, bov, tps....im not saying this is your problem but it might be worth checking. since then i have swapped to a hydra and gt3076r so i no longer have this problem at all. try a different piping on the inlet to the turbo. i had a straight pipe on mine too.

kungfoo2003

07-04-2009, 08:58 PM

I think that you are correct in thinking that this is fmic/bov related.
Now that I think about it, my car has a similar issue. Mine only happens on the highway, when i build a little bit of boost (say 5psi), and gently ease back on the gas, the car will buck a bit. It always seemed to me like this was happening because the bov was too tight (not too loose) and only blew off a small amount of boost when i ease of the gas. Ive gotten around this problem by adjusting my driving habits. I make sure to fully step off the gas to make the bov open more.

My piping is only 2.25in. At 2.75in I would think that you are getting a very exaggerated version of the same problem, because you are dealing with a much larger volume of air in your intercooler piping.

If you want to try another bov, Id look into the synchronic bov. That one seems to be the most responsive to small changes in throttle.

You have given me the best info thus far!

I think there is only 2 ways to solve this poblem:
Go standalone and eliminate the AFM
or get the Synapse BOV!

check out the video on this Synchronic BOV page.
Synapse BOV vid (http://synapseengineering.com/cart/products/Synchronic_BOV_Weld_Steel_Silver_Black-7-2.html)

This really illustrates something related to my problem. Listen to the "brand X" on the wrx in the vid while driving, and that is what my car sounds like most of the time under light and normal boosting conditions. It does it really bad when the bucking happens as well, so I'm leaning more towards this whole issue being greatly related to surge causing abnormal AFM operation.

I think I might try this Synapse BOV, as it has a normally open condition, which would more than likely erase my problem. This is exactly what I have been looking for! A normally open valve that closes when you need it to and does not allow any surge!

joe's gt

07-04-2009, 09:23 PM

Why aren't these more popular? They sound like the perfect scenario and cost just as much as an ssqv. I have never heard of one of these till now.

Lagos

07-05-2009, 03:11 AM

Why aren't these more popular? They sound like the perfect scenario and cost just as much as an ssqv. I have never heard of one of these till now.

Because 99% of people who are in the market for a bov are choosing their bov's based on the cool noise they make when they blow off.
The synchronic is probably the best functioning bov, but it cant be vented, and offers no cool ricer sound.

joe's gt

07-05-2009, 04:38 AM

Gotcha. I like the sound of mine personally, but I would gladly give that up for a better functioning recirc valve. Will stick with what works for now I guess.

kungfoo2003

07-05-2009, 05:38 AM

does it function like the stock mr2 bpv?

T-spoon

07-05-2009, 07:43 AM

Because 99% of people who are in the market for a bov are choosing their bov's based on the cool noise they make when they blow off.
The synchronic is probably the best functioning bov, but it cant be vented, and offers no cool ricer sound.

Pretty judgmental to call it a ricer sound, given that BOVs have an actual function, and most cars don't have performance issues venting to atmosphere, and most of the ones that do, you can avoid the problems by changing driving habits slightly. So.. if it has actual function, and just happens to make a sound someone likes, that doesn't make it ricer. So I think the real answer here is the syncronic has far less exposure in the market than names like HKS and Greddy and Blitz, not because most people choose to have their cars performing poorly just to make a loud sound.

Sang

07-05-2009, 05:04 PM

The synchronic is probably the best functioning bov, but it cant be vented

Yes, it can.

joe's gt

07-05-2009, 08:24 PM

Yes, it can.

^^ thats what I was thinking as well cuz it said that on the site.

trumanpriest

07-06-2009, 04:32 PM

I had the same issue on my CT-20B with 2.5" piping. Someone on at.com mentioned that some turbo's don't match with the aftermarket Downpipes quite right and that the wastegate doesn't open completely because clearance issues. I noticed that my problem went away when I changed my SSQV to a looser spring so it vents at lower boost.

kungfoo2003

07-16-2009, 10:59 PM

I installed the Synchronic BOV recirculated today using their HKS flange and 1" recirc fitting. It fixed everything completely!

joe's gt

07-17-2009, 12:18 AM

So erratic BOV was the culprit. Glad you found the problem. I really didn't think it was an issue with your afm.

T-spoon

07-17-2009, 01:42 AM

Toldja it wasn't the FMIC.... :hehe:

kungfoo2003

07-17-2009, 05:47 AM

Yah I really think there was some sort of surging happening around low vacuum, and since the SSQV is closed all the time, the surge caused erratic AFM operation.

This thing totally got rid of any surge I had previous, and it drives as smooth as a baby's bottom

Sean

07-17-2009, 08:45 AM

I will be doing this as well.

I know they have an anti stall kit so that you don't have to recirc it, I wonder how well that works.

Thanks for trying it out.

kungfoo2003

07-17-2009, 07:22 PM

Make sure you tighten the hose fittings and everything when you get the Synchronic. I found that some of the fittings on mine were loose out of the box